Several compositions are known to be recommended for artificial fish lures. The preferred composition and the standard for the recreation fishing industry are the polyvinyl chloride plastisols (PVC). PVC is ideally suited for formulating and molding soft lures. However, PVC has two major drawbacks: i) it does not biodegrade in the environment, nor is it digestible, and ii) it does not release fish attractants efficiently.
PVC is persistent in the environment and is not digestible by fish or animals. Fish are known to have completely blocked their digestive systems by consuming PVC lures, resulting in the death of the fish. PVC plastisol lures are comprised of polyvinyl chloride, hydrocarbon plasticizers, oil extenders and stabilizers. These compounds are not water-soluble and will persist in the lakes and rivers year after year. It is obvious that a biodegradable lure would be advantageous to the environment as well as to the fish that take the lure but are not caught or those that find and eat the lost lures.
PVC lures do not release active chemicals (attractants) very well, and generally from the surface of the lure only. Active chemicals present inside of a PVC lure are not released at all or at best are released at a very slow and ineffective rate from fish lures. Clearly a more efficient release of chemical attractants would be desirable.
Compositions have been described that could meet the biodegradable and release of attractant issues, but they do not address the necessary properties required of a soft recreational fishing lure. Additionally, they have disadvantages even within the technologies described.
U.S. Pat. No. 4,664,857 (Nambu) describes a method of making a hydrogel utilizing polyvinyl alcohol (PVA), carrageenan, xanthan, guar gum. The patent states that fish-luring agents may be used to formulate fish baits with this invention. However, Nambu teaches that vacuum dehydration while a molded object remains frozen (that is, freeze drying) is required to produce a hydrogel from PVA that is strong, elastic and water-resistant. A rehydration process is also called for. This vacuum dehydration and later rehydration is a time-consuming and costly process.
U.S. Pat. No. 3,875,302 (Inoue) describes a hydrogel made from PVA. It is stated that an artificial bait can be prepared. lnoue's teaching requires a freezing period of a minimum of two hours and up to fifty hours. This process is time- and cost-consuming. Inoue's technology cannot process PVA with a degree of polymerization above 2000, putting a significant limitation on developing lures that are as tough as or tougher than PVC lures.
U.S. Pat. No. 4,375,481 (Kuwabara) describes a product with an inner and an outer layer, which is targeted primarily as a human food, but a claim is made that the process can produce a fish bait. This process utilizes gums, starches, proteins, etc., and metal ions to effect chemical crosslinking. This gel form lacks the coadhesive strength to remain empaled on a fishhook while casting, trolling, and the like actions used in fishing. This technology also does not allow for a satisfactory combination of strength, elasticity and flexibility required for a satisfactory fishing lure. If the gel is made strong, the chemical bonds make the gel hard and stiff; if made soft and flexible, the gel is not strong enough. By nature of the crosslinking in the Kuwabara patent, elasticity is reduced.